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[ Upstream commit7b0c03ecc4] This patch adds a new device-tree property that allows to specify the dma protection control bits for the all of the DMA controller's channel uniformly. Setting the "correct" bits can have a huge impact on the PPC460EX and APM82181 that use this DMA engine in combination with a DesignWare' SATA-II core (sata_dwc_460ex driver). In the OpenWrt Forum, the user takimata reported that: |It seems your patch unleashed the full power of the SATA port. |Where I was previously hitting a really hard limit at around |82 MB/s for reading and 27 MB/s for writing, I am now getting this: | |root@OpenWrt:/mnt# time dd if=/dev/zero of=tempfile bs=1M count=1024 |1024+0 records in |1024+0 records out |real 0m 13.65s |user 0m 0.01s |sys 0m 11.89s | |root@OpenWrt:/mnt# time dd if=tempfile of=/dev/null bs=1M count=1024 |1024+0 records in |1024+0 records out |real 0m 8.41s |user 0m 0.01s |sys 0m 4.70s | |This means: 121 MB/s reading and 75 MB/s writing! | |The drive is a WD Green WD10EARX taken from an older MBL Single. |I repeated the test a few times with even larger files to rule out |any caching, I'm still seeing the same great performance. OpenWrt is |now completely on par with the original MBL firmware's performance. Another user And.short reported: |I can report that your fix worked! Boots up fine with two |drives even with more partitions, and no more reboot on |concurrent disk access! A closer look into the sata_dwc_460ex code revealed that the driver did initally set the correct protection control bits. However, this feature was lost when the sata_dwc_460ex driver was converted to the generic DMA driver framework. BugLink: https://forum.openwrt.org/t/wd-mybook-live-duo-two-disks/16195/55 BugLink: https://forum.openwrt.org/t/wd-mybook-live-duo-two-disks/16195/50 Fixes:8b3444852a("sata_dwc_460ex: move to generic DMA driver") Reviewed-by: Andy Shevchenko <andriy.shevchenko@linux.intel.com> Signed-off-by: Christian Lamparter <chunkeey@gmail.com> Signed-off-by: Vinod Koul <vkoul@kernel.org> Signed-off-by: Sasha Levin <sashal@kernel.org>
Linux kernel
============
There are several guides for kernel developers and users. These guides can
be rendered in a number of formats, like HTML and PDF. Please read
Documentation/admin-guide/README.rst first.
In order to build the documentation, use ``make htmldocs`` or
``make pdfdocs``. The formatted documentation can also be read online at:
https://www.kernel.org/doc/html/latest/
There are various text files in the Documentation/ subdirectory,
several of them using the Restructured Text markup notation.
See Documentation/00-INDEX for a list of what is contained in each file.
Please read the Documentation/process/changes.rst file, as it contains the
requirements for building and running the kernel, and information about
the problems which may result by upgrading your kernel.